improved error message in test_driver

theano/sandbox/cuda/tests/test_driver.py

@@ -28,7 +28,10 @@ def test_nvidia_driver1():
                         profile=False)
     topo = f.maker.fgraph.toposort()
     assert len(topo) == 2
-    assert sum(isinstance(node.op, B.GpuCAReduce) for node in topo) == 1
+    if sum(isinstance(node.op, B.GpuCAReduce) for node in topo) != 1:
+        msg = '\n\t'.join(['Expected exactly one occurrence of GpuCAReduce ' +
+            'but got:']+[str(app) for app in topo])
+        raise AssertionError(msg)
     if not numpy.allclose(f(), a.sum()):
         raise Exception("The nvidia driver version installed with this OS "
                         "does not give good results for reduction."